This invention relates to a process for preparation of high 1,4-cis polybutadiene and more particularly, to the process for preparing polybutadiene by polymerizing 1,3-butadiene monomer using a catalyst prepared by aging a mixture of a neodymium salt compound, a nickel salt compound represented by the following formula I, an organoaluminium compound and a borontrifluoride complex compound represented by the following formula II and formula III in the presence or absence of a conjugated diene compound. With much remarked catalytic activity, polybutadiene with a very high 1,4-cis content can be prepared in a high yield using a small amount of catalyst.
Ni(OOCxe2x80x94R)2xe2x80x83xe2x80x83Formula I
Wherein, R is an alkyl group, a cycloalkyl group, an aryl group or an arylalkyl group containing from 6 to 20 carbon atoms.
BF3OR1R2xe2x80x83xe2x80x83Formula II
wherein, R1 and R2, which can be the same or different, and are independent substituents, respectively, are alkyl or cycloalkyl groups containing from 1 to 10 carbon atoms. 
wherein, R3 is an alkyl group containing from 2 to 10 carbon atoms.
When polybutadiene is intended to be prepared via polymerization of 1,3-butadiene, the method of using lanthanum series metal catalyst, i.e., the elements from atom number 57 (La) to 71 (Lu), can provide diene polymer containing higher 1,4-cis content than other methods which comprise polymerizing one or more of conjugated dienes in the presence of transition metal compound such as nickel (Ni), titanium (Ti) and cobalt (Co).
Among lanthanum series metals, cerium(Ce), lanthanum(La), neodymium(Nd) and gadolinium(Gd) are known to have an excellent catalytic activity; among them, neodymium has the most excellent catalytic activity.
Many conventional methods for preparing polybutadiene (hereinafter referred to as xe2x80x9chigh cis-BRxe2x80x9d) using, lanthanum series metal as catalyst have been disclosed as follows:
i) a method of preparing high cis-BR in the presence of a catalyst prepared by mixing a neodymium salt compound, a silicon halide or an organosilicon halogen compound, an organoaluminium compound and a diene compound, followed by the aging process [PCT No. 93-05083];
ii) as the case of using a mixture containing more than two rare earth metal salts, a method of preparing high cis-BR in the presence of a catalyst prepared by mixing a didymium salt compound, an organoaluminium compound and a Lewis acid, followed by the aging process. Here, the term didymium stands for a mixture of 72% of neodymium, 20% of lanthanum and 8% of praseodymium [U.S. Pat. Nos. 4,242,232, 4,260,707];
iii) a method of preparing a modified high cis-BR with excellent characteristics in such a manner that 1,3-butadiene is polymerized using a catalyst prepared by mixing a rare earth metal salt compound, a Lewis acid and/or Lewis base and organoaluminium compound in the presence or absence of diene compound, followed by the aging process; then some modifying compounds selected from the following components such as isocyanate, carbon disulfide, epoxy compound or organotin halide compound are added to the high cis-BR (U.S. Pat. Nos. 4,906,706, 5,064,910);
iv) a method of preparing high cis-BR in the presence of a catalyst prepared in such a manner that neodymium hydride, chlorine donor compound and electron donor ligand are reacted, followed by the addition of organoaluminium compound [U.S. Pat. No. 4,699,962];
v) a method of polymerizing 1,3-butadiene using a neodymium salt compound, an organic halide compound, an organic compound having hydroxyl group and an organoaluminium compound [Europe Patent No. 127,236];
vi) a method of preparing high cis-BR in the presence of an improved catalyst prepared in such a manner that a neodymium salt compound, an organic halide compound and an organoaluminium compound are mixed, followed by the aging process at lower than 0xc2x0 C. [Europe Patent No. 375,421 and U.S. Pat. No. 5,017,539]; and,
vii) a method of preparing high cis-BR in the presence of a catalyst prepared by mixing a neodymium salt compound, an organoaluminium compound, tris(pentafluorophenyl)boron or its derivative in the presence or absence of diene compound, followed by the aging process [Europe Patent No. 667,357].
However, the conventional methods have some difficulty in preparing polybutadiene to satisfy simultaneously both high 1,4-cis content and yield using a small amount of catalyst.
To comply with the aforementioned problems that the prior arts have encountered, the inventor et al. have made intensive studies and noted that high cis-BR can be prepared in a high yield using a catalyst prepared by aging a mixture of a neodymium salt compound, a nickel salt compound represented by the formula I, an organoaluminium compound and a borontrifluoride complex compound represented by the formula II and formula III. In consequence this invention is completed.
Therefore, an object of this invention is to provide a process for preparing polybutadiene with a very high 1,4-cis content in a high yield by polymerizing 1,3-butadiene in the presence of a catalyst consisting of a neodymium salt compound as a rare earth element metal and a nickel salt compound as a transition metal. With much remarked catalytic activity, polybutadiene with a very high 1,4-cis content can be prepared in a high yield using a small amount of catalyst.
To achieve the above objective, this invention is characterized by process for preparing polybutadiene by polymerizing 1,3-butadiene in a nonpolar solvent in the presence of a catalyst prepared by aging a mixture of a neodymium salt compound, a nickel salt compound represented by the following formula I, an organoaluminium compound and a borontrifluoride complex compound represented by the following formula II and formula III in the presence or absence of a conjugated diene compound.
Ni(OOCxe2x80x94R)2xe2x80x83xe2x80x83Formula I
Wherein, R is an alkyl group, a cycloalkyl group, an aryl group or an arylalkyl group containing from 6 to 20 carbon atoms.
BF3OR1R2xe2x80x83xe2x80x83Formula II
wherein, R1 and R2, which can be the same or different, and are independent substituents, respectively, are alkyl or cycloalkyl groups containing from 1 to 10 carbon atoms. 
wherein, R3 is an alkyl group containing from 2 to 10 carbon atoms.
This invention is explained in more detail as set forth hereunder.
The neodymium salt compound used in this invention is preferably carboxylate compound having a good solubility in non-polar solvents. For example, the neodymium compound includes compound selected from the group of neodymium hexanoate, neodymium heptanoate, neodymium octanoate, neodymium octoate, neodymium naphthenate, neodymium stearate and neodymium versatate; a carboxylate compound having more than 6 carbon atoms is preferred as the neodymium salt compound.
According to this invention, it is preferred to use a carboxylate compound as the nickel salt compound represented by the formula I, one of the active ingredients of catalyst, since it contains a ligand which has a good solubility to a nonpolar solvent. The examples of the nickel salt compound include nickel hexanoate, nickel heptanoate, nickel octanoate, nickel octoate, nickel naphthenate, nickel stearate and nickel versatate; a carboxylate compound having more than 6 carbon atoms is preferred as the nickel salt compound
The examples of the borontrifluoride complex compound represented by the formula and formula III include borontrifluoride-dimethylether, borontrifluoride-diethylether, borontrifluoride-dibutylether and borontrifluoride-tetrahydrofuran.
Further, the examples of the commonly available organoaluminium compound include trimethylaluminium, triethylaluminium, tripropylaluminium, tributylaluminium, triisobutylaluminium, trihexylaluminium, trioctylaluminium and triusobutylaluminium hydride.
The polymerization catalyst for the manufacture of polybutadiene is prepared by aging a mixture of a neodymium salt compound, a nickel salt compound, an organoaluminium compound and a borontrifluoride complex compound. Hence, a nonpolar solvent should be selected as a solvent for aging the catalyst so as not to react with the catalyst. It is preferred to use cyclohexane, hexane, heptane or toluene as a nonpolar solvent.
Meantime, during the aging process of catalyst, the nickel salt compound represented by the formula I is mixed with the neodymium salt compound in the molar ratio of 1:20xcx9c20:1, preferably in the molar ratio of 2:8xcx9c8:2. If the ratio deviates the above range, the reaction yield becomes poor.
Further, the organoaluminium compound is mixed with the neodymium salt compound in the molar ratio of 1:1xcx9c200:1, preferably in the molar ratio of 10:1xcx9c150:1. If the ratio deviates the above range, the reaction yield is drastically-reduced or polymer having low molecular weight is generated.
Also, the borontrifluoride complex compound is mixed with the neodymium salt compound in the molar ratio of 0.1:1xcx9c10:1, preferably in the ratio of 0.5:1xcx9c5:1. If the ratio deviates the above range, the reaction yield becomes poor.
Further, the conjugated diene compound is mixed with the neodymium salt compound in the molar ratio of 1:1xcx9c30:1, preferably in the molar ratio of 2:1xcx9c10:1. If excess of the conjugated diene compound beyond the above range is employed, the viscosity of catalyst solution has increased.
The procedure for preparing an aging catalyst is that a neodymium compound solution in the presence or absence of a small portion of 1,3-butadiene is placed in a catalyst reactor under nitrogen atmosphere, followed by the addition of the nickel salt compound represented by the formula I, the organoaluminium compound and the borontrifluoride complex compound represented by the formula II and formula III. The aging of catalyst can be made in such order of addition or in modifying order.
After each compound is added to the reactor, the mixed catalyst is under the aging process. The aging process is performed at xe2x88x9220xcx9c60xc2x0 C. for 5 minutes to 10 hours, preferably at 0xcx9c50xc2x0 C. for 30 minutes to 2 hours. Thus the catalyst for polymerizing 1,3-butadiene is prepared.
1,3-butadiene monomer is polymerized using the catalyst, so prepared, to give polybutadiene with a very high 1,4-cis content according to this invention. The non-polar solvent used for the polymerization of 1,3-butadiene contains at least one or more of aliphatic hydrocarbons (e.g., butane, pentane, hexane, isopentane, heptane, octane and isooctane); cycloaliphatic hydrocarbons (e.g., cyclopentane, methylcyclopentane, cyclohexane, mcthylcyclohexane and ethylcyclohexane); aromatic hydrocarbons (e.g., benzene, toluene, ethylbenzene or xylene).
Since any nonpolar solvent used for this invention may significantly affect the polymerization, it should be added to the reactor after oxygen and water are entirely removed with this in mind, the polymerization of this invention is performed under a high-purity nitrogen atmosphere; the appropriate reaction temperature is from room temperature to 100xc2x0 C. The polymerization is made for 2 hours under appropriate catalytic conditions to give polybutadiene in a high yield over 90%. The polymerization is completed by introducing polyoxyethyleneglycolether organophosphate as a reaction terminator and 2,6-di-t-butyl-p-cresol as a stabilizer. The resulting polybutadiene is precipitated with methanol or ethanol.
This invention is explained in more detail by the following examples but is not confined by these examples.